I haven't played a game on a computer since Doom back in the 90's. Heard some friends talking about Age of Empire? I enjoy most games that involve weapons, was addicted to Halo 3 when it came out but since then I haven't played much.
Recently, I've been playing League of Legends. It's free and it's pretty fun. Sometimes you can get some pretty crappy teammates, but overall I'm enjoying it.
Borderlands is only 7.50 for the game of the year version (including all 4 addons) this weekend on steam. It looks like a lot of fun and if you like weapons, I dont think you will find a game with more of them.
If you don't want to spend money, just play some stuff at www.kongregate.com. Love it. I've been playing ShellShock recently (basically it's Scorched Earth, if you ever played that).